As we draw electric current from the Daniel cell, the concentration of $\left[{\mathrm{Zn}}^{2+}\right]$ gradually___________ and the concentration of $\left[{\mathrm{Cu}}^{2+}\right]$ gradually___________

increases, decreases

 $$\begin{gathered} {\mathrm{Zn}}_{\left(\mathrm{s}\right)}\to {\mathrm{Zn}}_{{ }^{\left(\mathrm{aq}\right)}}^{2+}+2{\mathrm{e}}^{-1}; \\ {\mathrm{Cu}}_{{ }^{\left(\mathrm{aq}\right)}}^{2+}+2{\mathrm{e}}^{-1}\to {\mathrm{Cu}}_{\left(\mathrm{s}\right)}; \end{gathered}$$ 

 The half-cell reactions responsible for generation of electric current are as follows: As more ${\mathrm{Zn}}^{2+}$ ions are produced, its concentration increases. As ${\mathrm{Cu}}^{2+}$ions are consumed, its concentration decreases.